Acute kidney injury (AKI), previously known as acute renal failure is a major public health concern and is one of the most serious complications of hospitalized patients. The study of population epidemiology of AKI is relatively novel, in contrast to the well-defined epidemiology of end-stage renal disease (ESRD) by the United States Renal Data System. The past decade has also witnessed major advances in our understanding of the population epidemiology of chronic kidney disease, as a result of analyses of nationally representative databases such as the National Health and Nutrition Examination Surveys. Our overall goal is to elevate the study of AKI epidemiology to a comparable level of sophistication. The three specific aims of this proposal are: Aim 1: To determine the population incidence rate of dialysis-requiring AKI in the United States. We hypothesize that the incidence rate of dialysis-requiring AKI has increased at a rapid rate in recent years and now exceeds the incidence rate of ESRD requiring renal replacement therapy. Aim 2: To determine whether the burden of disease for dialysis-requiring AKI is particularly high in clinically important subgroups. We hypothesize that the growth in the incidence of dialysis-requiring AKI has been disproportionally greater in certain subgroups, such as African-Americans, the elderly, and patients with diabetes mellitus. Aim 3: To correlate secular trends in the incidence of dialysis-requiring AKI with secular trends in several diseases states and medical interventions among hospitalized patients that are risk factors for AKI. We hypothesize that the growth in the incidence of dialysis-requiring AKI parallels the rising incidence of sepsis, hospitalization for acute heart failure, expanded utilization of cardiac catheterization, intensive care and mechanical ventilation.